Electric heating device and method of making same



ELECTRIC HEATING DEVICE AND METHOD OF MAKING SAME Filed Feb. 4, 1953,

INVENTORS B OSCAR BECK huamr L. BECK m CECIL H GUNTHORP Patented Nov.1936 UNITED STATES ELECTRIC HEATING DEVICE AND METHOD OF MAKING SAMEBjorn Oscar Beck and Hubert L. Beck, Chicago, and Cecil H. Gunthorp, DesPlaines, Ill.

Application February 4, 1933, Serial No. 655,154

4 Claims.

Our invention relates to electric heating devices and more especially toheating elements for stoves, flat irons, curling irons and the like.

It is an object of our invention to provide a 5 simple, practical, andefficient device of the character described.

It is another object of our invention to provide a heating device whichis adapted for a quick transfer of heat from the resistor element to thesurface plate or other point of utilization.

.A further object is to provide a heating device in which the resistorelement is cast into a metal surface plate or outer jacket in order toobtain a superior heat conducting contact with the same.

A still further object is to provide a heating device by the method ofapplying an insulating coating to a resistor wire, hardening saidcoating and embedding the resistor in a cast metal.

Other objects and advantages will appear and be brought out more fullyin the following specification, reference being had to the accompanyingdrawing, in which Fig. 1 is a plan view partly in section of an embodiment of our invention;

Fig. 2 is a sectional elevation taken along the line 2-2 of Fig. 1;

Fig. 3 is a perspective view partly in section of a modification, and

Fig. 4 is a partial sectional view in enlargement showing the resistorelement, its insulating coating and the casting in which the same isembedded.

Heretofore in the manufacture of electrical heating devices for ordinaryuse such as stoves, flat irons, curling irons and the like, a difficultyusually encountered has been the inability to satisfactorily insulatethe resistor element from the surface plate or material to which theheat is to be conducted and at the same time obtain an efficient mediumof heat transfer between these two parts of the device. A furtherdifficulty usually presented is the necessity of embedding the resistorso far from the surface of utilization of the heat that an undesirablelength of 45 time is required for the transfer of heat between them.

We are aware that some attempts have been made to overcome theseobjections and difficulties such as disclosed in United States PatentNo.

50 1,654,292 issued to A. D. Keene et al. in which a coating of alundumor aluminum oxide is applied to a resistor wire and located in groovesin a carbonaceous material. The alundum becomes powdery, leaving airspaces therein and defeat- 55 ing to a considerable extent the purposefor which it is intended to be used. Our invention is a particularimprovement on this feature and we provide a resistor coating of ceramicmaterial such as the porcelain group which can be embedded in a castblock and make a highly efficient heat transfer contact between the wireand the heating surface. This ceramic insulation can be applied in aliquid form and hardened or dried and cast within a metallic material.This ceramic insulation does not change its physical 10 character whichis a solid with practically no air content and is such that it willprovide a highly efficient transfer of heat. This insulation may be of aceramic cement, which upon hardening assumes many of the characteristics15 of ordinary porcelain. It may be chiefly fused aluminum oxide soldunder the trade name Alundum", magnesium oxide, silicon oxide or othersuitable ceramic materials held together by a binding material such assodium silicate, 2O potassium silicate, bentonite, sillimanite, aceramic cement sold under the trade name Insolute, or any other suitablebinding material or combination of several. suitable binding materials.25

Referring more partciularly to the drawing, we show a heating unithaving a cooking surface or utilization plate I, which may be of castiron, cast steel, cast aluminum, or other suitable metal which may becast, poured, or molded into 0 the desired form to produce a suitableouter jacket. Using ,cast iron as the example, plate I is secured to aheat resisting base 2, as by bolts 3, which also serve as terminals fora resistor conductor 4, having a ceramic insulated coating 5 separatingthe resistor from plate 4. The base 2 may be of any suitable materialssuch as asbestos composition, porcelain, lava, or the like. A protectinglayer of insulation is shown at 6 as a guard for the connections ofconductor '4 with 40 bolts 3. Resistor 4 is shown near the top of plateI, which is made possible by this type of casting, and provides for aminimum heat passage path from source to the point of utilization.Insulation 5 is preferably of ceramic material such as Insolute orliquid porcelain, which is applied to the conductor in liquid orsemi-liquid form and which, upon hardening forms an insulation similarto ordinary porcelain.

In the manufacture of our heating unit the conductor will first beshaped as desired, and given its ceramic insulation by painting,spraying, dipping or drawing through a bath while the conductor iseither hot or cold. After the insulation has hardened, plate I is formedby casting or molding the metal around the conductor, as may be done byconventional methods. After the cooling, or set, the insulation 5 willmake a sealed or solid contact between conductor l and plate I,permitting a high rate of heat transfer therebetween.

In Fig. 3 we show a modification wherein the conductor 1, insulated asabove, is helical and laid in a groove 8, and the cast surface plate 9cast to fill the space in the grooves not occupied by the conductor I.We have found that in the spiral form the insulation is less likely tocrack than when the conductor is straight. If desired a metal core tothe surface of which has been applied a ceramic insulation, may belocated within the helical conductor I, the latter also having appliedto its surface the ceramic insulation above described. Then the metal ofthe plate 9 is cast around the core and the conductor to intimatelycontact or seal with both.

In Fig. 4 we show an enlargement of the helical wire iesistor II! withits ceramic coated insulation ll, cast into a bar or rod I2, as it willbe appreciated that the heating or surface member may be of a variety ofshapes or configurations to form an outer jacket suitable for variouspurposes.

We claim:

1. An electric heating device comprising an electric conductor to thesurface of which is bonded a solid coating of an electricallynonconductive and heat conductive ceramic sub-' stance, a refractoryplate having a groove in which said coated conductor is located, and asurface plate of cast metal having a portion thereof extending into saidgroove and around said coated conductor and in which said coatedconductor is sealed and embedded and to which said coating is bonded.

2. An electric heating device comprising a core, an electric conductoraround said core and having a solid coating of an electricallynon-conductive and heat conductive ceramic substance, and a cast metaljacket embedding and sealing said coated conductor and said corc thereinand being bonded thereto to form an integral unit.

3. An electric heating device comprising a core having a solid surfaceportion of an electrically non-conductive and heat conductive ceramicsubstance, and an electric conductor around said core and having a solidcoating of an electrically non-conductive and heat conductive ceramicsubstance, and a cast metal jacket embedding and sealing said coatedconductor and said core therein and being bonded thereto to form anintegral unit.

4. An electric heating device comprising a metal core having a solidcoating of an electrically non-conductive and heat conductive ceramicsubstance, and an electric conductor around said core and having a solidcoating of an electrically non-conductive and heat conductive ceramicsubstance, and a cast metal jacket embedding and sealing said coatedconductor and said core therein and being bonded thereto to form anintegral unit.

B. OSCAR BECK. HUBERT L. BEcKe CECIL H. GUNTHORP.

